Modified preamble for programmable transmitter

• US 20060274852A1
• Filed: 04/11/2006
• Published: 12/07/2006
• Est. Priority Date: 06/07/2005
• Status: Active Grant

• Current Assignee: Broadcom Corporation (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Hansen, Christopher J., Trachewsky, Jason A., Moorti, Rajendra Tushar
• Granted Patent: US 7,558,537 B2
• Time in Patent Office: Days
• US Class Current: 375/295
• CPC Class Codes: H04L 1/0002 by adapting the transmission rate
• CPC Class Codes: H04L 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 1/06 using space diversity
• CPC Class Codes: H04L 27/2613 Structure of the reference signals

Abstract

A programmable transmitter generates a frame preamble to train a receiver with respect to a communication link format that corresponds to a transmission mode wherein the transmission mode may comprise transmitting the communication link over one or more antennas. Generally, the invention includes generating a preamble with an arrangement that depends upon whether a Greenfield (high data rate) or mixed mode transmission is to occur and that depends upon a number of spatial streams that are to be generated. One format for high data rate transmission includes a short training sequence, a long training sequence and a signal field. The mixed mode transmission further includes a legacy prefix.

Claims

1. A transmitter, comprising:

a baseband processor operable to generate one or more outgoing digital signal streams for transmission over one or more antennas substantially at the same time according to a selected transmission mode of operation;

wherein the baseband processor defines logic for generating a preamble for each outgoing digital signals stream according to whether a high data rate or mixed mode transmission format is to be used for the outgoing digital signal streams; and

wherein, for a high data rate transmission format, the preamble format comprises;

a 24 microseconds period if only one stream is to be transmitted; and

a 24 microsecond periods plus 4 microseconds for each additional stream that is to be transmitted.

2. The transmitter of claim 1 wherein the format for the preamble for one stream includes fields for a short training sequence, a first long training sequence, and a signal field.

3. The transmitter of claim 2 wherein the preamble format fields are arranged sequentially, relative to each other, in the order of short training sequence, the first long training sequence, and signal field.

4. The transmitter of claim 2 wherein the preamble format comprises a 28 microsecond period and a second long training sequence following the signal field.

5. The transmitter of claim 4 wherein the preamble format comprises a 32 microsecond period and a third long training sequence following the second long training sequence.

6. The transmitter of claim 5 wherein the preamble format comprises a 36 microsecond period and a fourth long training sequence following the third long training sequence.

7. The transmitter of claim 1 wherein each preamble format comprises a period that is approximately a whole multiple of 4.0 microseconds.

8. The transmitter of claim 1 wherein, for a mixed mode transmission format, the preamble format comprises:

a 36 microsecond period if only one stream is to be transmitted; and

a 36 microsecond period plus 4 microseconds for each additional stream that is to be transmitted.

9. The transmitter of claim 8 wherein the format for the preamble for one stream includes fields for carrying legacy information, a signal field, a short training sequence, and a first long training sequence.

10. The transmitter of claim 9 wherein the preamble format fields are arranged sequentially, relative to each other, in the order of legacy information, the signal field, the short training sequence, and the first long training sequence.

11. The transmitter of claim 10 wherein the preamble format comprises a 40 microsecond period and a second long training sequence following the signal field.

12. The transmitter of claim 11 wherein the preamble format comprises a 44 microsecond period and a third long training sequence following the second long training sequence.

13. The transmitter of claim 12 wherein the preamble format comprises a 48 microsecond period and a fourth long training sequence following the third long training sequence.

14. The transmitter of claim 10 wherein the first long training sequence is one of 4 or 8 microseconds long.

15. The transmitter of claim 8 wherein the short training sequence and each long training sequence is phase shifted in the frequency domain by performing a cyclic shift of a series of samples in the time domain.

16. The transmitter of claim 8 wherein the signal field is generated with a rotated BPSK modulation.

17. The transmitter of claim 8 wherein, for a plurality of streams, each short training sequence is an orthogonal sequence relative to each of the other short training sequences.

18. The transmitter of claim 8 wherein, for a plurality of streams, each long training sequence is an orthogonal sequence relative to each of the other long training sequences.

19. The transmitter of claim 1 wherein the short training sequence and each long training sequence is phase shifted in the frequency domain by performing a cyclic shift of a series of samples in the time domain.

20. The transmitter of claim 1 wherein the signal field is generated with a rotated BPSK modulation.

21. The transmitter of claim 8 wherein, for a plurality of streams, each short training sequence is an orthogonal sequence relative to each of the other short training sequences.

22. The transmitter of claim 8 wherein, for a plurality of streams, each long training sequence is an orthogonal sequence relative to each of the other long training sequences.

23. A transmitter operable to generate a preamble having a preamble format comprising:

a first stream utilizing a legacy long training sequence;

a short training sequence;

a first long training sequence

a second long training sequence utilizing a phase shifted legacy long training sequence phase shifted by a first value relative to the first long training sequence.

24. The transmitter of claim 23 wherein the preamble format further includes a third long training sequence utilizing a phase shifted legacy long training sequence phase shifted by a second value relative to the first long training sequence.

25. The transmitter of claim 24 wherein the preamble format further includes a fourth long training sequence utilizing a phase shifted legacy long training sequence phase shifted by a third value relative to the first long training sequence.

26. The transmitter of claim 25 wherein the phase shifts are created by introducing cyclic delays of first, second and third values of samples in the time domain.

27. The transmitter of claim 26 wherein each long training sequence is orthogonal relative to each of the other long training sequences.

28. The transmitter of claim 23 wherein the pre-amble further includes a signal field that defines transmission parameters for outgoing transmissions.

29. The transmitter of claim 28 wherein the signal field is generated as a rotated BPSK signal.

30. The transmitter of claim 28 wherein every field of the preamble has a period that is approximately equal to whole multiple of 4.0 microseconds.

31. A method for transmitting a preamble for one of a high data rate or mixed mode outgoing transmission, comprising:

for an outgoing transmission comprising only one stream transmitted on only one antenna, generating a preamble comprising a short training sequence, a long training sequence, and a signal field, in that order;

for an outgoing transmission comprising two streams transmitted on two antennas, generating a preamble comprising a short training sequence, a first long training sequence, a signal field, and a second long training sequence, in that order; and

for an outgoing transmission comprising three streams transmitted on three antennas, generating a preamble comprising a short training sequence, a first long training sequence, a signal field, a second long training sequence, and a third long training sequence in that order.

32. The method of claim 31 for an outgoing transmission wherein, for an outgoing transmission comprising three streams transmitted on three antennas, generating a preamble comprising a short training sequence, a first long training sequence, a signal field, a second long training sequence, a third long training sequence, and a fourth training sequence, in that order.

33. The method of claim 31 for an outgoing transmission wherein, for an outgoing transmission comprising four streams transmitted on four antennas, generating a preamble comprising a short training sequence, a first long training sequence, a signal field, a second long training sequence, a third long training sequence, and a fourth training sequence, in that order.

34. The method of claim 32 wherein each field within the outgoing transmission comprises a period that is approximately equal to a whole multiple of 4.0 microseconds.

35. The method of claim 31 wherein the preamble format includes long training sequences wherein each long training sequence is phase shifted and orthogonal relative to the other long training sequences.

36. The method of claim 35 further comprising generating a signal field, wherein the signal field is generated as a rotated BPSK signal.